1. Field of the Invention
The present invention relates to an electrophotographic image forming device, such as a laser beam printer, a copying machine, or a facsimile device. More particularly, the invention relates to a process unit detachably loaded into the image forming device and a structure of the image forming device for receiving and accommodating the process unit.
2. Description of the Related Art
Conventional image forming devices, such as a laser beam printer, uses a process unit. The process unit is, for example, a combined unit of a photosensitive unit and a developing unit. The photosensitive unit includes a photosensitive drum and a charger. The developing unit includes a developing roller and a toner cartridge containing developing agent (toner) therein.
During the printing operation, the developing roller is urged against the photosensitive drum, so that the developing roller transfers toner onto the photosensitive drum. Also, the transfer roller is urged against the photosensitive drum.
For the sake of maintenance and for facilitating paper jam resolving job, the process unit is detachably mounted on the image forming device. That is, the process unit is unloaded from and loaded into the image forming device when paper jam occurs, for example.
U.S. Pat. No. 6,101,350 proposes horizontally loading the process unit. The horizontally loading type requires a locking mechanism to prevent the loaded process unit from being accidentally detached. To withstand strong detaching force to be imparted upon the process unit, a rigid locking mechanism is needed. However, the image forming device cannot be structurally simplified and made compact in size and also the cost of the image forming device cannot be lowered if the rigid locking mechanism is employed.
The present intention has been made to solve the aforementioned problems, and accordingly it is an object of the invention to provide an image forming device and a process unit in which the process unit can be easily loaded into the image forming unit and the process unit thus loaded cannot be easily detached.
Another object of the invention is to provide a process unit in which a developing unit can be easily mounted on and dismounted from a photosensitive unit.
Still another object of the invention is to provide an image forming device that has a simple structure for receiving a process unit and urging the developing roller against the photosensitive drum once the process unit is received and accommodated in a process unit accommodating section.
To achieve the above and other objects, there is provided, according to one aspect of the invention, an image forming device that includes a housing, a pair of first guides, a process unit, a process unit accommodating section, and a second guide. The first guides extend down to terminals. The process unit has a bottom wall and side walls. The side walls are formed with protrusions protruding outward. The protrusions are engageable with the first guides, and guided down along the first guides toward the terminals when the process unit is loaded into the housing. The process unit accommodating section is provided for receiving and accommodating the process unit. The second guide is formed between the first guides for guiding the bottom surface of the process unit from a top open space of the housing toward the terminal. The process unit is accommodated in the process unit accommodating section when the protrusions of the process unit have brought into abutment with the terminals and a trailing end of the process unit is rotated downward about an imaginary line connecting the protrusions.
With the image forming device thus constructed, the process unit can be easily accommodated in the process unit accommodating section. This can be done by engaging the protrusions with the first guide and placing the process unit on the second guide. When the protrusions formed in the process unit are brought into abutment with the terminals, the trailing end of the process unit is automatically rotated downward due to its own weight and accommodated into the accommodating section. Also, the process unit can be easily unloaded from image forming device by lifting the trailing end of the process unit, placing it on the second guide, and moving up along the second guide.
A posture maintaining member may be formed on the process unit for maintaining a posture of the process unit when accommodated in the process unit accommodating section.
Preferably, the first guide is in the form of an elongated U-shaped groove into which the protrusion is inserted, and the second guide is in the form of a rail having an upper flat surface on which the process unit slidably moves.
A locking mechanism may further be provided for locking the process unit to the housing. It is desirable that the locking mechanism be provided in the process unit accommodating section. The locking mechanism may be constructed to resiliently engage the trailing end of the process unit.
The process unit includes a photosensitive unit and a developing unit. The developing unit is detachably mounted on the photosensitive unit. The photosensitive unit includes a photosensitive drum, and the developing unit includes a developing roller. The protrusions are provided to the photosensitive unit. The rotational shaft of the photosensitive drum may be provided to project from the photosensitive unit. In such a case, the projected portions of the rotational shaft may be used as the protrusions.
A latching mechanism may be further provided for latching the process unit to the process unit accommodating section.
The process unit includes a photosensitive drum and developing roller. It is desirable that the process unit is accommodated in the process unit accommodating section while being urged toward a predetermined direction to urge the developing roller against the photosensitive drum.
The process unit may be formed with auxiliary guide members for determining a loading direction and unloading direction of the process unit when loading into and unloading from the housing.
It is desirable that the developing unit have a bottom surface on which a first posture maintaining member is formed for maintaining a posture of the developing unit when mounted on the photosensitive unit and that the photosensitive unit have a bottom surface on which a second posture maintaining member is formed for maintaining a posture of the photosensitive unit when accommodated in the process unit accommodating section. Preferably, the first posture maintaining member and the second posture maintaining member are mated with each other.
According to another aspect of the invention, there is provided an image forming device that includes a housing, a process unit, a process unit accommodating section, and developing roller moving mechanism. The housing has a pair of upstanding walls each formed with a first guide extending to a first terminal. The process unit is detachably mounted on the housing. The process unit includes a photosensitive unit and a developing unit. The photosensitive unit has at least a photosensitive drum and first projections. The first projections are engageable with the first guides. The first protrusions are guided down along the first guides toward the first terminals when the process unit is loaded into the housing. The developing unit has at least a developing roller. The process unit accommodating section is provided for receiving and accommodating the process unit. The process unit is accommodated therein when a trailing end of the process unit is rotated downwardly about an imaginary line connecting the protrusions that are located in the first terminals. The developing roller moving mechanism is provided for moving the developing roller toward the photosensitive drum. At this time, the developing roller is urged against the photosensitive drum.
With the image forming device thus constructed, when the developing roller is urged against the photosensitive drum by the developing roller moving mechanism, the photosensitive unit is also urged in the same direction in which the developing roller is urged and thus can be set to a predetermined position.
The photosensitive unit is detachably mountable on the process unit accommodating section when the photosensitive unit is loaded into the housing from a top open space of the housing. Also, the developing unit is detachably mountable on the photosensitive unit mounted on the process unit accommodating section. Accordingly, exchange of the developing unit can be easily performed.
It is desirable that the developing unit be formed with an engagement protrusion. The engagement protrusion is brought into engagement with the developing roller moving mechanism when the process unit is accommodated in the process unit accommodating section.
The developing unit has a second protrusion. Also, a guide groove is formed in the photosensitive unit. The guide groove extends to a second terminal near the first terminals and guides the second protrusion to the second terminal. When a trailing end of the developing unit is rotated downward when the second protrusion is located in the second terminal, then the engagement protrusion is brought into engagement with the developing roller moving mechanism.
A separation mechanism may further be provided for moving the developing roller away from the photosensitive drum. Also, a nipping mechanism may further be provided for nipping the engagement protrusion. The developing roller moving mechanism and the separation mechanism may be used as the nipping mechanism.
Alternatively, the nipping mechanism may include a first nipping member having a first movable end, and a second nipping member having a second movable end. The engagement protrusion is nipped when the first movable end and the second movable end move toward each other. An open space is provided between the first movable end and the second movable end when the first movable end and the second movable end move away from each other. Accordingly, the nipping mechanism can easily grasp the engagement protrusion when the developing unit is downwardly moved. The developing roller moving mechanism may include an urging member that urges the first nipping member toward the second nipping member to thereby urge the developing roller against the photosensitive drum. The separation mechanism may include a moving member that moves the second nipping member toward the first nipping member to thereby move the developing roller away from the photosensitive drum.
It is desirable that each of the side walls of the developing unit be formed with the engagement protrusion. In this case, the developing roller moving mechanism and the separation mechanism are provided at each side of the pair of upstanding walls so as to engage the engagement protrusion formed in each side wall of the developing unit.
It is further desirable that the housing be formed with a pair of second guides between the first guides for guiding the process unit from the top open space of the housing toward the process unit accommodating section.
The first guide shaft may be a rotational shaft of the photosensitive drum and the second guide shaft a rotational shaft of the developing roller.
According to further aspect of the invention, there is provided an image forming device that includes a housing, a photosensitive unit, a developing unit, a pair of first guides, a photosensitive unit accommodating section, and a pair of guide grooves. The housing has first side walls. The photosensitive unit has second side walls. The developing unit has third side walls. Further, the photosensitive unit has a photosensitive drum and a first guide shaft projecting out from the second side walls. The developing unit has a developing roller and a second guide shaft projecting out from the third side walls. The developing unit is detachably mounted on the photosensitive unit.
Each first guide is formed in each first side wall and extends to a first terminal. The first guide serves to guide the first guide shaft therealong to the first terminal when the photosensitive unit is loaded into the housing from a top open space of the housing.
The photosensitive unit accommodating section is provided for receiving and accommodating the photosensitive unit. The photosensitive unit is accommodated therein when a trailing end of the photosensitive unit is rotated downward about the first guide shaft located in the first terminals.
Each guide groove is formed in each second side wall and extends to a second terminal. The guide groove serves to the second guide shaft therealong to the second terminal. The photosensitive unit has a developing unit mounting section for mounting the developing unit. The developing unit is mounted thereon when it is loaded into the housing from the top open space of the housing along the guide grooves to the second terminals. The first guides are formed substantially in parallel to the guide grooves.
According to the image forming device thus constructed, the developing unit can be mounted on or dismounted from the photosensitive unit regardless of whether the photosensitive unit is loaded into or unloaded from the image forming device. Further, the combined unit in which the developing unit is mounted on the photosensitive unit can be easily loaded into or unloaded from the image forming device at a time.
It is desirable that the photosensitive unit be provided with locking mechanism for locking the developing unit mounted on the developing unit mounting section to the photosensitive unit. Preferably, the locking mechanism is provided to a rear wall of the photosensitive unit. Accordingly, when the developing unit is locked to the photosensitive unit with the locking mechanism, both the photosensitive unit and the developing unit can be carried and moved by grasping only the photosensitive unit or the developing unit. The developing unit can easily be dismounted from the photosensitive unit merely by unlocking the locking mechanism.
The locking mechanism has a locking position for locking the developing unit to the photosensitive unit accommodated in the photosensitive unit accommodating section and an unlocking position for unlocking the developing unit from the photosensitive unit accommodated in the photosensitive unit accommodating section. As such, the developing unit can be easily mounted on and dismounted from the photosensitive unit while leaving the photosensitive unit in the photosensitive unit accommodating section.
The developing unit is pivotally movable about the second guide shaft when both end portions of the second guide shaft are located in the second terminals. Accordingly, the developing unit can be easily mounted on and dismounted from the photosensitive unit by grasping the rear end of the developing unit, orienting the second guide shaft downward, and moving the second guide shaft along the guide grooves formed in the photosensitive unit. In this case, the photosensitive unit may be accommodated in the photosensitive unit accommodating section or may be unloaded from the image forming device and placed outside the image forming device.
An urging mechanism may further be provided for urging the developing the developing roller against the photosensitive drum. By slidably moving the first guide shaft of the photosensitive unit along the first guides, the photosensitive unit is automatically accommodated in the photosensitive unit accommodating section due to its own weight when the first guide shaft is brought into abutment with the first terminals. Once the photosensitive unit is accommodated in the accommodating section, the photosensitive. Unit is not allowed to shift horizontally. Therefore, the photosensitive unit cannot be not easily taken out from the loaded position. In this condition, when the developing unit is mounted on the photosensitive unit, the urging mechanism urges the developing unit so that the developing roller is urged against the photosensitive drum. This means that the photosensitive unit is also urged by the urging mechanism and is set to a predetermined position.
The first guide shaft may be a rotational shaft of the photosensitive drum and the second guide shaft a rotational shaft of the developing roller. In this case, a center of the second guide shaft is substantially located on an imaginary line connecting a center of the first guide shaft and a point where the urging mechanism urges the developing unit.
Because the first guides are formed substantially in parallel to the guide grooves and also because there is the geometric relationship as described above, the loading of the photosensitive unit and mounting of the developing unit on the loaded photosensitive unit can be performed substantially in the same fashion.
The developing unit may be formed with an engagement protrusion. The engagement protrusion is brought into engagement with the urging mechanism when a trailing end of the photosensitive unit with the developing unit mounted on the developing unit mounting section is rotated about the first guide shaft located in the first terminals.
With such an arrangement, the engagement protrusion formed in the developing unit is automatically brought into engagement with the urging mechanism simply by accommodating the photosensitive unit in the photosensitive unit accommodating section. As such, positioning the photosensitive unit and urging the developing roller against the photosensitive roller can be achieved with one-touch operation.
The engagement protrusion is preferably formed in each third side wall. Accordingly, urging force imparted upon the photosensitive drum becomes uniform in its lengthwise direction.
According to further aspect of the invention, there is provided there is provided a photosensitive unit capable of being loaded into and unloaded from an image forming device. The photosensitive unit includes a case, a photosensitive drum rotatably disposed in the case; and projections. Each projection projects out from the side wall of the case. The projections are engageable with a pair of guides formed in the side walls of the housing. The projections are guided down along a pair of guides formed in the housing of the image forming device toward the terminals. The case is accommodated in the photosensitive unit accommodating section when the protrusions have brought into abutment with the terminals and a trailing end of the case is rotated downward.
According to further aspect of the invention, there is provided a developing unit capable of being mounted on and dismounted from a photosensitive unit. The developing unit includes a case, a developing roller rotatably disposed in the case, a protrusion, and an engaging member. The protrusion projects out from the side wall of the case. The projection is engageable with a guide formed in the photosensitive unit. The projection is guided down along the guide toward the terminal. The case is mounted on the developing unit mounting section when the projection has brought into abutment with the terminal and a trailing end of the case is rotated downward. The engaging member engages an urging mechanism provided in an image forming device. The urging mechanism urges the case toward the photosensitive unit when the case is mounted on the developing unit mounting section.
According to yet further aspect of the invention, there is provided a developing unit that is similar to the one described above but different therefrom in that the projection is guided down along the guide toward the terminal in a direction substantially in coincident with the direction in which the projections of the photosensitive unit are guided down along the guides formed in the side walls of the image forming device and in that a locking projection is formed in the trailing end of the case. The locking projection is engageable with a locking lever provided in the image forming device. Only the case can be dismounted from the developing unit mounting section by disengaging the locking lever from the locking projection while leaving the photosensitive unit in the image forming device.
According to yet further aspect of the invention, there are provided process unit that combinations of the photosensitive unit and the developing unit described above.